[1 + 4]-Cycloaddition of a stable silylene to 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene

Abstract

The stable bis(amino)silylene Si[(NCH 2 Bu t ) 2 C 6 H 4 -1,2] 1 undergoes [1 + 4]-cycloaddition with 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene 2 to afford compound 3: the molecular structure of 3 is supported by NMR spectroscopic data and confirmed by a single crystal X-ray diffraction study.

Synthesis of the 2,4,5‐Tri‐tert‐butyl‐1,3‐diphospholide Anion by Phosphinidene Elimination from 2,4,6‐Tri‐tert‐butyl‐1,3,5‐triphosphabenzene on Treatment with the Amide Li[NPh(SiMe3)]

“…] and 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene, P 3 C 3 tBu 3 (in a 1:2 ratio), afforded equimolar amounts of the lithium salt of the five-membered 2,4,5-tri-tert-butyl-1,3-diphospholide ring anion LiP 2 C 3 tBu 3 (isolated as its TMEDA adduct) and the tricyclic compound 6-[phenyl(trimethylsilyl)-amino]-3,5,7-tri-tert-butyl-1,2,4,6-tetraphosphatricyclo-[3.2.0.0 2,7 ]hept-3-ene. The first step in the reaction is the extrusion of a stabilised aminophosphinidene from the aromatic six-membered ring, resulting in the stable, aromatic fivemembered diphospholide anion.…”

“…] (2 a) with P 3 C 3 tBu 3 (1 a) in a 1:2 ratio in THF at 50 8C for three days readily afforded the lithium salt of the 1,3-diphospholide anion, LiA C H T U N G T R E N N U N G [P 2 C 3 tBu 3 ] (3 a) in quantitative yield together with the unusual tricyclic compound 6-[phenyl(trimethylsilyl)amino]-3,5,7-tri-tert-butyl-1,2,4,6-tetraphosphatricyclo[3.2.0.0 2,7 ]hept-3-ene (4 a) (Scheme 2).…”

“…Likewise, complexes containing h 6 -phosphinines catalyse the synthesis of pyridines from alkynes and nitriles [5] and the cyclodimerisation of 1,3-butadiene. [6] In previous studies [7][8][9][10] we showed that the 2,4,6-tri-tertbutyl-1,3,5-triphosphabenzene, P 3 C 3 tBu 3 (1 a), readily undergoes [1 + 4] cycloaddition reactions with isoelectronic silylenes and (transition-metal-complexed) phosphinidenes (and in unpublished work [11] ) with isolobal In I and Ga I compounds. On the other hand, the analogous reaction of 1 a with the Arduengo-type carbene, tetramethylimidazol-2-ylidene, unexpectedly led to a ring contraction reaction involving the extrusion of a CtBu fragment from the 2,4,6-tri-tertbutyl-1,3,5-triphosphabenzene ring leading to the quantitative formation of the aromatic five-membered 1,2,4-triphosphole, P 3 C 2 tBu 2 (carbene), ring system.…”

1,4‐Addition of Grignard Reagents to 2,4,6‐Tri‐tert‐butyl‐1,3,5‐triphosphabenzene

“…Thus, for example, DielsAlder reactions [5] or addition reactions of lithium alkoxides with participation of all three PÀC double bonds [6] occur readily under mild conditions. Compound 1 also reacts readily with silylenes, [7] carbenes, [8] or phosphinidenes, [9] usually through a [2þ1]-cycloaddition process.…”

1,4‐Addition von Grignard‐Reagentien an 2,4,6‐Tri‐tert‐butyl‐1,3,5‐triphosphabenzol

“…B. DielsAlder-Reaktionen [5] oder Lithiumalkoholat-Additionen unter Beteiligung aller drei P-C-Doppelbindungen [6] bei milden Bedingungen leicht durchführbar. Auch mit Silylenen, [7] Carbenen [8] oder Phosphinidenen [9] reagiert 1 bereitwillig, meist unter [2þ1]-Cycloaddition.Wir haben das Triphosphabenzol 1 mit den GrignardReagentien 2 a-d in THF umgesetzt und konnten nachweisen, dass 2 a-d schon bei À16 8C regio-und stereoselektiv mit 1 in einer formalen 1,4-Addition reagiert. Die Regioselektivität resultiert aus der Polarität der P-C-Doppelbindung, [10] wonach der organische Rest R der Grignard-Verbindung an ein Phosphoratom und das Metall an die C-4-Position addiert.…”